Development of an OTR beam profile monitor for 3-50 beam transport line in J-PARC

A Beam Profile Monitor using the Optical Transition Radiation (OTR) in the beam transport line (3-50BT) between 3GeV Rapid-cycling synchrotron (RCS) and 50GeV Main ring (MR) has been planned in the J-PARC. The OTR monitor is conventionally used as a quasi-nondestructive, two-dimensional beam profile monitor for a beam having larger γ (above 10). Since the γ of beam is 4.2, opening angle the OTR is very wide in our case, and optics with extremely wide acceptance will be necessary for effective-extraction of the OTR from target. For this purpose, we placed a target (aluminum foil, 10μm thickness) normal to the beam orbit, and collecting the back emitted OTR by Offner type mirror system. The Offner system is designed to collect 500mrad opening angle of OTR, and enough good field of 100mm x 100mm for large beam size (about 60mm in diameter). The summary of the plan of the OTR profile monitor and selection of it's location, and development of the Offner system are described in this paper. (author)